JP2843670B2 - Method of coating steel substrate using low temperature plasma treatment and primer treatment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to the use of low temperature plasma technology for corrosion protection of steel. The novel method of the present invention involves plasma treatment of steel with a reactive or inert gas, followed by plasma thin film deposition of organosilane on the treated substrate (this is performed at ambient temperature and does not require baking). , And ultimately, the application of appropriate primers. The deposition process of the present invention is performed at ambient temperature, utilizes DC power using a steel substrate as the cathode, and the anode is provided with a magnetically reinforced member (magnetron).

BACKGROUND OF THE INVENTION Corrosion protection of steel substrates is an important industrial method. This method is important for many industries, including the automotive and steel industries. Currently, the most common methods of corrosion protection of steel substrates are galvanizing, zinc phosphate treatment, electrodeposition of organics, conventional spray or dip priming, oil painting, and the like. However, in the automotive industry and other high performance applications, these methods have the following problems: (1) volatile organics (VO
Contamination in the form of C), (2) disposal of large amounts of waste, (3) unsuitable for the coating of recessed surfaces, and (4) insufficient long-term corrosion protection.

Plasma thin film deposition is a uniform deposition,
It is known to produce extremely dense film layers without "pinholes" and with good edge coverage. Further, this method does not use a solvent, so that there is no VOC problem. Most applications of the plasma deposition area have been limited to small articles (eg, microelectronic components). Plasma treatments for larger parts have been used primarily for plastic substrates.

It has been disclosed that it is possible to deposit polymer thin films on metal substrates. Plasma deposition of organic films on metals is described in the Journal of the Oil and C
This is described in a paper entitled "Surface Coating of Metal in Glow Discharge" (hereinafter referred to as "glow discharge") in our Chemist Association, Vol . 48, (1965). This paper uses glow discharge (ie, plasma deposition) for short term protection of steel substrates, organic vapors (styrene, acrylate, butadiene, diethyl silicate, and tetraethyl orthosilicate).
A method for coating a metal substrate with a polymer thin film derived from Co., Ltd. is generally described. Although this method uses AC power and a system pressure of 1-5 Torr, the steel is reacted with a reactive gas (eg, oxygen) or an inert gas (eg,
(Argon) or mixtures thereof are not disclosed. The "glow discharge" method will not be a viable method for long-term corrosion protection of the steels required for the automotive industry.

Professor Yasuda has published the Journal of Applied Polymer Science: App
lied Polymer Symposium 42,233 (1988), a paper entitled Plasma Polymerization at Total Energy Input for Metal Protective Coatings,
Several substrates for organosilane deposition and oxygen cleaning of steel substrates are disclosed. However, this article does not disclose the method of the invention of applying organosilane to an organosilane membrane or using a primer.

Prof. Yasuda is J.Vac.Sci.Technol.A7 (2) Mar / Apr
(1989) published a paper on the use of magnetrons in plasma polymerization in a paper on plasma polymerization by magnetron glow discharge, I, Effect of magnetic fields on monomer decomposition at low pressures. However, this paper again discusses only AC power, not DC power. It was previously thought that when a magnetron was used in a DC power system, the magnetron would only act as a cathode and not as an anode (the thin film method published by Vossen and Kern (1978), p. Section).

The use of polysiloxane as a glow discharge deposited film for corrosion protection of steel is also disclosed in Aoki Japanese Patent Application No. 51-83030 (hereinafter Aoki patent). Further, this specification teaches the use of AC power, but does not teach or suggest pretreating the steel with a reactive gas or an inert gas plasma. This Aoki
The patented technology does not appear to have utility as a long-term corrosion protection method for automotive steel plates to solve the problem of adhesion.

What is needed is a method of depositing an organic thin film layer that provides improved corrosion resistance to a variety of different steel substrates. This method results in a film with good adhesion, good edge coverage, good barrier properties, and should reduce VOC problems and minimize waste disposal.

SUMMARY OF THE INVENTION It has been found that the corrosion resistance of steel can be improved by performing the following methods: (1) pretreating the steel substrate with a reactive or inert gas plasma; Using DC power of 100-2000 volts, preferably 300-1200 volts; (3) making the steel substrate a cathode;
(4) Attach a magnetic enhancement member (ie, magnetron) to the anode; and (5) use organosilane vapor (with or without a reactive or inert gas) as the plasma gas to be deposited. It has good coverage (good edge coverage and no pinholes), minimal deposition of anodes or chamber walls (which is a problem when using alternating current), and is faster than done with alternating current power A plasma thin film deposition rate is obtained. If the plasma thin film layer is subsequently coated with a primer coating, the corrosion protection is particularly pronounced.

It has also been found to be advantageous to perform another plasma deposition on the first layer deposited or to perform a post-treatment on the surface of the plasma layer before coating with the primer coating. This post-processing step can be performed to enhance the adhesion between the plasma thin film and the plasma coating. This post-treatment of the plasma layer in turn forms groups such as hydroxyls, acids or bases that can react with the primer coating, causing polarization on the surface of the preferred plasma thin film layer. The post-treatment step typically requires a reactive plasma gas such as oxygen, water, ammonia or the like or an inert plasma gas such as helium, argon or the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a plasma deposition system of the present invention showing a vacuum chamber, electrodes, power supplies, associated piping, and the like.

FIG. 2 is a front view of one of the anodes equipped with the magnetron.

 FIG. 2A is the same side view of the anode as FIG.

DETAILED DESCRIPTION OF THE INVENTION It has been found that a simple coating system, including plasma treatment, is an effective way to protect steel surfaces from corrosion. The novel system of the present invention is suitable for use on a variety of different types of steel of various sizes and shapes (eg, bare steel, cold rolled steel, stainless steel, galvanized steel, phosphatized steel, etc.). It is convenient. For example, a pre-assembled vehicle body, vehicle body parts, rolls, coils, sheets, and the like.

The novel system of the present invention consists of four basic steps. The first step is a pretreatment of the steel substrate with an inert or reactive plasma gas. The second step is plasma deposition of a thin film. The third step (optional step) is a post-plasma treatment of the thin film surface. The fourth step is coating of the post-treated plasma thin film with a primer.

The first step, which includes a plasma pretreatment with an inert or reactive gas, is preferred over conventional cleaning and results in better adhesion. (If there is oil on the steel substrate, it should be cleaned in a conventional manner, for example with a solvent, before this plasma treatment).

After a plasma pretreatment of an inert or reactive gas, a second
The process involves coating a steel substrate with a thin layer of plasma-generated polymer in a highly evacuated chamber. An optional third step after plasma deposition is a post-treatment of the surface of the film to enhance the adhesion between the plasma thin film and the primer coating applied thereon. Post treatment of this plasma layer then produces functional groups that can react (or be compatible) with the plasma coating, such as hydroxyl, acid or base. Post-treatment steps typically include a plasma gas, such as oxygen, water, ammonia, or the like, or an inert plasma gas, such as helium, argon, or the like.

The fourth step, application of a primer, can be performed by various methods. The important thing is to choose a primer that has good adhesion to the plasma deposited thin film, good barrier properties and good corrosion protection.

Step 1: Plasma Pretreatment An overall view of the preferred system of the present invention is shown in FIG.
(Note: This diagram is merely illustrative of the invention, which will enable those skilled in the art to design many effective systems for practicing the invention.) For example, plasma pre-treatment and plasma deposition could be performed in separate rooms in a continuous process. FIG. 1 shows a vacuum chamber 11 , a cathode 12 (this is a steel substrate), an anode 1
3 , a power supply 14 , a plasma gas supply line 15 , a plasma gas flow controller 16 and a vacuum pump 17 are shown. The cathode of the DC power supply 14 is connected to the steel substrate to form the cathode 12 . The grounded anode of the DC power supply 14 is connected to the anode 13 . Second
As shown in the figure, the anode 13 has a superposed magnetic field (magnetron).
It has. (A magnetron is essential for the plasma deposition process, but not for the plasma pre- or post-plasma process). If a magnetron is used in the plasma deposition process, the magnetic field on the magnet surface should be between 10 and 10,000 gauss, preferably between 100 and 1000 gauss and most preferably between 700 and 900 gauss. Magnetrons are well known in the art,
II-2 and II-4 of the book entitled "Thin Film Method"
Department has been announced. As is apparent in the art, there are many ways to superimpose the magnetic field.

FIG. 2 shows the details of the arrangement of the anode used in the embodiment of the present invention. (The exact dimensions are described in detail in the Examples section). The anode 13 comprises an aluminum plate 23 ; a titanium plate 22 (which is mounted inside the aluminum plate 23 ); an iron ring 24 and an iron disk 24 ' (which is mounted behind the aluminum plate 23). There are) and eight permanent bar magnets 25 (this is mounted on an iron disk 24 ' and an iron ring 24 with the South Pole facing the center point). Preferred magnetic field strengths are in the range of 700-900 Gauss. Next, the electrode (anode) 13 is made entirely of ceramic material
Supported by 26 . As will be apparent to those skilled in the art, the structure of the anode can vary as well as the materials of construction of the anode. For example, the titanium plate 23 or aluminum plate 22 may be another paramagnetic material having a low sputtering yield, such as an iron disk 24 ' or an iron ring.
24 may be another ferromagnetic material.

To perform the plasma pretreatment and plasma deposition steps, the steel substrate is suspended centered between two parallel anodes 13 and connected to the cathode of a DC power supply 14 such that the steel substrate is the cathode 12 . (In an industrial system, it would be possible to attach the anode to the robot arm to cover complex shapes. The number, size and shape of the anodes and their location could be varied depending on the desired application. ).

Next, the vacuum chamber 11 is evacuated using the vacuum pump 17 until the system pressure becomes lower than 1 mTorr. Regardless of the gas flow rate, the system pressure is adjusted at the throttle valve 18 using a pressure gauge 19 reading. The pretreatment gas (for example, oxygen gas or a mixture of oxygen gas and argon) is supplied to the vacuum chamber 11 at a desired flow rate while maintaining the pressure at 1 Torr or less, preferably less than 100 mTorr. The preferred pretreatment gas of the present invention is oxygen because it removes organic contaminants and can form metal oxides on the surface of the steel substrate. Other reactive or inert gases or mixtures thereof can also be used. These other pretreatment gases include air, hydrogen, nitrogen, argon, water vapor and the like.

Operating parameters for low-temperature plasma processing are joules / kg
Can be provided at the energy input level per mass of W / FM plasma gas given by: Where W is the power input into the system (W = joules / sec) and F
Is the molar flow rate and M is the molecular weight of the gas. (FM stands for mass flow rate). According to this relationship, the flow rate used depends on the power input and the molecular weight of the gas. The energy input per mass is between 1 megajoule and 1 kg
Should be between 2 gigajoules per kg.

The pretreatment plasma gas is supplied through a plasma gas supply line 15 and the flow rate is adjusted using a suitable plasma gas flow controller 16 . Next, the power supply 14 is turned on to start the plasma state. The power is then adjusted to the desired power level. This power level varies depending on the flow rate, the size of the substrate, the distance between the cathode and the anode, the molecular weight of the pretreatment gas, the pressure, and the like. The pretreatment plasma should be maintained for the desired time (typically 30 seconds to 10 minutes),
The power supply 14 must then be turned off and the pretreatment gas flow must be stopped using a suitable plasma gas shutoff valve 20 . The processing time depends on the operation parameter W / FM. Effective processing can be performed between 0.5 gigajoules / sec / kg and 50 gigajoules / sec / kg by “energy input × processing time ÷ mass”. Vacuum chamber after pre-treatment plasma process
The vacuum pump 11 is evacuated once again using the vacuum pump 17 to a pressure of 1 mTorr or less. This ends the plasma pretreatment process. Note: It would also be possible to use AC or RF power instead of DC power for the plasma pretreatment step.

Process 2: Plasma Polymer Deposition The basic concept of plasma deposition is Academic Press
In 1985, Professor Yasuda's book entitled Plasma Polymerization. This is done by supplying plasma deposition gas at a desired flow rate through plasma gas flow controller 16 to vacuum chamber 11 . As in the case of the pretreatment plasma, the flow rate depends on the power used in the system and the molecular weight of the plasma gas. The energy input per mass is 1 megajoule and 1 kg per kg depending on the plasma deposition gas and the input level used.
Should be between 1 gigajoule per. It is important to keep the system pressure between 1 mTorr and 1 Torr, preferably between 10 mTorr and 500 mTorr, and most preferably between 20 mTorr and 100 mTorr while supplying the plasma deposition gas to the vacuum chamber 11. . As described above, the pressure of the system is regulated by a throttle valve 18 using a reading from a pressure gauge 19 , independent of the gas flow rate.

Once the desired flow rate and system pressure are achieved, power is turned on and then adjusted to the desired power level. This power level varies depending on the flow rate, the size of the substrate, the distance between the cathode and the anode, the molecular weight of the plasma gas, the pressure, and the like. The plasma deposition should last for the desired time to obtain the desired thin film properties and thickness. Thin film thickness is 10
It ranges between Angstroms to 10 microns, preferably from 10 Angstroms to 5,000 Angstroms, and most preferably from 10 Angstroms to 3,000 Angstroms. Deposition time is typically 1 second to 20
Minutes, preferably 30 seconds to 10 minutes, most preferably 30 seconds to 2 minutes. The control of the deposition process may be based on “energy input × deposition time / mass”. 0.5 gigajoules / sec per kg and 50 per kg
It should be kept between gigajoules / sec. After the desired time, the DC power supply 14 must be turned off and the plasma gas flow must be stopped using a suitable plasma gas stop valve 20 . Deposition time is based on input level, expressed in joules per kg, divided by mass. The effective plasma deposition time for corrosion resistance depends on thin film adhesion, thin film barrier properties and thin film thickness.

The preferred plasma deposition gas of the present invention is trimethylsilane (TMS). Other gases include dimethylsilane (DMS), tetramethylsilane, trimethylethoxysilane, methyltrimethoxysilane, hexamethyldisiloxane or any of silicon, oxygen, carbon, phosphorus or hydrogen or mixtures thereof, and Examples include, but are not limited to, organosilanes with or without vinyl unsaturation.
Other hydrocarbons, including carbon, hydrogen, oxygen, fluorine or mixtures thereof (eg, methane) can also be used. In addition, organometallic compounds including antimony, phosphorus, zinc, titanium, aluminum, tin, zirconium and other metals or mixtures thereof can be used.

Further, it is advantageous to use a carrier gas (particularly when a high-boiling compound vapor is used) as the plasma deposition gas. The carrier gas may be an inert gas such as, for example, argon and helium, or a reactive gas (or a mixture thereof) such as, for example, oxygen or nitrogen.

Liquid or even solid compounds can be used as plasma deposition compounds provided that sufficient vapor pressure is generated to supply those compounds to a vacuum system. Gaseous materials at room temperature are preferred for the purpose of maintaining a constant flow rate.

After the deposition step, the vacuum chamber 11 should be evacuated using a vacuum pump 17 to a pressure of 1 mTorr or less.
This ends the deposition process. However, it should be pointed out that a further layer of plasma thin film can be deposited on the first layer. These subsequently deposited layers will likely be organic compounds other than silane or organometallic compounds. As described above (ie, DC power with a magnetron at the anode), it is essential to deposit the first layer, but the subsequently deposited plasma layer can be deposited by other power means known in the art (eg, AC power). , Ultra-high frequency and high frequency (RF) power.

Step 3: Surface Treatment of Deposited Thin Film The third step in the method of the present invention is an optional step of post-treating the surface of the deposited plasma thin film. This step is important because post-treatment of the surface of the deposited plasma thin film layer before it is covered by the primer coating can enhance the adhesion between the plasma thin film layer and the primer coating. However, in some cases, it may be desirable to skip the post-treatment step of the plasma thin film surface and proceed directly to the primer coating step for economic reasons (i.e., shorter processing times for higher productivity). . The post-treatment of the plasma thin film layer preferably produces hydroxyl groups, oxygen or chlorinated groups (eg, amines, alkylamines, amides, etc.) to polarize the surface. This post-treatment step typically involves the use of another non-polymerizable reactive gas, such as oxygen, water, carbon dioxide, or ammonia (or mixtures thereof), with or without an inert gas. Includes plasma treatment. An example of post-treatment of a plasma thin film is shown in Example V. It may also not be possible to generate polar groups on the surface of the plasma thin film by chemical methods, drying or wetting. This will be readily understood by those skilled in the art. For example, it is possible to treat the surface of the plasma thin film with chromic acid to generate hydroxyl groups or acid groups on the surface of the plasma thin film, or to sulfonate the surface with a sulfurous anhydride gas. (Polymer Interfac by Marcel Dekker, Inc.
e and Adhesion, (1982), p. 284, section 9.1.2).

Step 4: Applying a Primer After thin film plasma deposition and post-treatment of the surface of the plasma thin film, a conventional primer coating coating is applied. Although the steel substrate with the plasma deposited thin film has better corrosion protection than the same steel without the thin film, the corrosion resistance is surprisingly improved after application of the primer coating. Similarly, steel substrates using both the plasma-deposited thin film layer and the primer coating have better corrosion protection than steel substrates using only the primer coating.

The primer may be applied by any of a number of different methods well known in the art (eg, canode or anodic electrodeposition, dipping, spraying, rolling, powder coating, vacuum deposition polymerization, etc.). Can be. In addition, some of the many different primer coatings well known in the art can also be used. Examples include acrylic silane, polyester silane, polyester urethane silane, melamine / polyester, melamine / polyester urethane, epoxy anhydride, epoxyamine,
Examples thereof include, but are not limited to, polyester isocyanate and polyether vinyl.

Preferred primer coatings are those that can react with the plasma deposited thin film. Plasma-deposited thin film is treated with organosilane or post-treatment,
In the case of an organosilane having a hydroxyl group formed on the surface, the primer is preferably an acrylic silane, polyester silane or polyester urethane silane (that is, a primer having a silanol and alkoxysilane group). The most preferred primer is trimethoxysilane containing resin. Primers of this type are described in Kanegafuchi Patent No. US 4,801,658.

The primer formulation may or may not contain a catalyst (or promoter), such as a dialkyltin oxide compound, water, acid, or an organotitanate or organozirconate.

The thickness of the primer can vary very widely. Although a 2.5 to 125 micron thick primer film can be coated on the steel sheet, the preferred thickness range is 10.0 to 50 microns.

After primer deposition, a top coat can be applied subsequently. These include primer surfacers, monocoats, basecoat / clearcoats or any other topcoat systems known in the art.

EXAMPLES Unless otherwise stated, all examples were run as described in the Detailed Description section. More detailed data on the examples are given below: (1) Steel substrate: size (4 "x 6" x 0.032 ") If this has an oil content, it should be pre-washed with a solvent.

(2) Vacuum chamber: Pyrex glass bell with diameter 18 "and height 30".

(3) Power supply: External DC power supply (Advan as model MDX-1K)
ced Energy Industries, Inc.).

(4) Electrode description:-The cathode is the steel substrate described above, placed between two anodes.

Two anodes as shown in FIG. Each anode is an aluminum plate 23 (7 "x 7" x 1/2 "), a titanium plate (7" x 7 "x 1/16") mounted inside the aluminum plate 23 , and an iron ring 24 (outside). 7 "in diameter, 5.5" in inner diameter, 1/16 "thick) and an iron disk 24 ' mounted on the back side of the aluminum plate 23
(Diameter 2 ", thickness 1/16") and eight permanent bar magnets 25 (3 "x 1/2") mounted on iron disk 24 ' and iron ring 24 with the South Pole toward the center. × 1/4 ″).
The strength of the magnetic field ranges from 700 to 800 Gauss. The electrode (anode) 13 is entirely supported by a ceramic material 26 .

The cathode is located 2 "apart and between the two parallel anodes with the titanium side facing the cathode;

(5) Vacuum pump mechanism: mechanical booster pump (model available in series with mechanical rotary pump (available from Sargent-Welch Scientific Company as model 1376))
(Available from Shimadzu Corporation as MB-100F).

(6) Pressure gauge: capacitance pressure gauge (available from MKS Instruments as model 220BA).

(7) Throttle valve (available from MKS Instruments as model 253A) and throttle valve controller (also model 25
2A available from MKS Instruments).

(8) Flow controller: Mass flow controller (available from MKS Instruments as Model 1259B).

Explanation of corrosion resistance test (Scab test) Mark the test panel. The scribe line is at the center of the panel and is about 3 inches long. The scribed panel is then subjected to the next test cycle.

Monday to Friday: Soak in 5% sodium chloride solution for 15 minutes.

 Dry at room temperature in air for 75 minutes.

 Exposure to an environment of 85% relative humidity and 60 ° C for 22:30 minutes.

Saturday and Sunday: Samples are kept in a humid chamber (85% relative humidity, 60 ° C). Inspect samples occasionally. After the Scab corrosion test is completed, remove the test panel from the chamber and rinse with warm water. The samples were visually inspected for defects such as corrosion, build-up, peeling, reduced adhesion, or blisters. To evaluate the creep shrinkage (loss of adhesion between the primer and the steel sheet) due to the scribe line corrosion, the distance between the scribe line and the unmodified primer is measured. Calculated as the average of multiple measurements.

Example I Bare Steel Substrate / Oxygen Plasma Pretreatment / TMS Plasma Deposition / Silane Primer Substrate: Clean Cold Rolled Billet (Product Name, GMC 92A)
Oxygen plasma pretreatment conditions: DC power was 12 watts and between 600 and 800 volts; energy input per mass was 0.25 gigajoules per kg; oxygen gas flow rate was The system pressure was 30 mTorr; the output time was 2 minutes.

Deposition of plasma poly (trimethylsilane) using trimethylsilane (TMS) gas: DC current was 2 watts, 600-750 volts; energy input per mass was 24 gigajoules / kg; TMS gas flow rate Was 1.5 standard cubic centimeters per minute (sccm), the system pressure was 50 mTorr, and the output time was 2 minutes.

Application of primer coating: The substrate was removed from the vacuum chamber and the primer was applied. The primer applied was the primer most preferred by the present invention having a methoxysilane functional group. This resin is patented by Kanegafuchi Patent N
o US 4,801,658. The primer was applied to a thickness of 17.5 microns to 27.5 microns by dipping a steel substrate into the primer. Then at 200 ° F 30
Cured for minutes.

The samples were then subjected to the corrosion test described above for 5 weeks.
Adhesion was good by tape test (ASTM D3359).
The average creep distance was 1.5 mm and there was no blister. The non-uniform coverage of the green primer, not due to the plasma deposition layer, resulted in slight corrosion of the green. This problem changes the method of applying the primer (for example,
Vacuum deposition polymerization or electrodeposition coating).

Example II Zinc phosphate treatment, chromic acid washed steel / oxygen plasma pretreatment / TMS plasma deposition / silane primer Substrate: zinc phosphate treatment, steel washed with chromic acid solution (product name, GMC 92C; C168 C20) Available as DIW from ACT Corp.) Oxygen plasma pretreatment conditions: DC power 12 watts, 600
~ 800 volts: 1 kg energy input per mass
Was 0.25 gigajoules per second; the oxygen gas flow rate was 2 standard cubic centimeters per minute (sccm);
30 mTorr; and the output time was 2 minutes.

Deposition of plasma poly (tolmethylsilane) using trimethylsilane gas: DC power 2 watts, 60
0-750 volts; energy input per mass is 1k
The TMS gas flow rate was 1.5 standard cubic centimeters per minute (sccm), the system pressure was 50 mTorr, and the output time was 2 minutes.

Application of primer coating: The substrate was removed from the vacuum chamber and the primer was applied. The primer applied was the primer most preferred by the present invention having a methoxysilane functional group. This resin is a Kanegafuchi patent N
o US 4,801,658. The primer was applied to a thickness of 17.5 microns to 27.5 microns by dipping a steel substrate into the primer. Then at 200 ° F 30
Cured for minutes.

The samples were then subjected to the corrosion test described above for 5 weeks.
Adhesion was good by tape test (ASTM D3359).
The average creep distance was 0.9 mm and there was no blister. Very slight corrosion was observed, probably due to uneven coating of the edge primer, not due to the plasma deposition layer. This problem could be eliminated by changing the primer application method (for example, vacuum deposition polymerization or electrodeposition).

Example III Zinc phosphate treated, chromic acid washed galvanized steel substrate / oxygen plasma pretreatment / TMS plasma deposition / silane primer Substrate: zinc phosphate treated, chromic acid solution washed galvanized steel (product name, GMC 90E) Electro G1V70 / 70; C168 C20 DIW
(Available from ACT Corp.) Oxygen plasma pretreatment conditions: DC power 12 watts, 600
~ 800 volts; energy input per mass is 1kg
0.25 gigajoules per second; oxygen gas flow rate was 2 per minute
Standard cubic centimeters (sccm); system pressure was 30 mTorr; and output time was 2 minutes.

Deposition of plasma poly (trimethylsilane) using trimethylsilane gas: DC power 2 watts, 60
0-750 volts; energy input per mass is 1k
The TMS gas flow rate was 1.5 standard cubic centimeters per minute (sccm), the system pressure was 50 mTorr, and the output time was 2 minutes.

Application of primer coating: The substrate was removed from the vacuum chamber and the primer was applied. The primer applied was the primer most preferred by the present invention having a methoxysilane functional group. This resin is patented by Kanegafuchi Patent N
o US 4,801,658. The primer was applied to a thickness of 17.5 microns to 27.5 microns by dipping a steel substrate into the primer. Then at 200 ° F 30
Cured for minutes.

The samples were then subjected to the corrosion test described above for 5 weeks.
Adhesion was good by tape test (ASTM D3359).
The average creep distance was 1.2 mm and there was no blister. Very little corrosion was observed, probably due to non-uniform primer coating at the edges, not due to the plasma deposition layer. This problem could be eliminated by changing the different primer application methods (for example, vacuum evaporation polymerization or electrodeposition).

Example IV Galvanized Steel Substrate / Oxygen Plasma Pretreatment / TMS Plasma Deposition / Vacuum Deposited Organic Thin Film Primer Substrate: Galvanized Steel (Product Name, GMC 90E Elec Zin)
c Available from ACT Corporation as G70 / 70; clean) Oxygen plasma pretreatment conditions: DC power 12 watts, 600
~ 800 volts; energy input per mass is 1kg
Was 0.25 gigajoules per second; the oxygen gas flow rate was 2 standard cubic centimeters per minute (sccm);
30 mTorr; and the output time was 2 minutes.

Deposition of plasma poly (tolmethylsilane) using tolmethylsilane gas: DC power, 80 at 12 watts
0-950 volts; energy input per mass is 144 per kg
Megajoules; TMS gas flow rate was 1.5 standard cubic centimeters per minute (sccm); system pressure was 50 mTorr and output time was 2 minutes.

Application of primer coating: Organic thin film primer coating is made of Parylene C compound (Nova Tran Cor
Journal of Pol, entitled "Polymerization of Paraxylene Derivatives (for Parylene), Deposition Kinetics of I, Parylene N and Parylene C"
ymer Science (Polymer Chemistry version, vol. 22, (1984) p.
475 to 491).
The primer was applied to a thickness of 10.0 microns at room temperature.

The sample was then subjected to the corrosion test described above for about 5 weeks. Adhesion was good by tape test (ASTM D3359). The average creep distance was 1.4 mm and there was no blister. The edge had very good corrosion resistance.

Example V Bare Steel Substrate / Oxygen Plasma Pretreatment / Methane Plasma Deposition / Carbon Dioxide Plasma Posttreatment / Electrodeposited Primer Substrate: Bare Steel (Product Name, GMC 92A Available from ACT Corp .: Clean Cold Rolled Steel This example shows that the post-treatment of the plasma thin film layer is an easy-to-perform alternative and results in improved corrosion resistance.

Enzyme plasma pretreatment conditions: DC power 12 watts, 600
~ 800 volts; energy input per mass is 1kg
0.25 gigajoules per second; oxygen gas flow rate was 2 per minute
Standard cubic centimeters (sccm); system pressure was 50
And the output time was 2 minutes.

Deposition of plasma methane polymer using methane gas.

DC power was 5 watts, 500-600 volts; energy input per mass was 0.21 gigajoules / kg; methane gas flow rate was 2 standard cubic centimeters per minute (sccm)
The system pressure was 50 mTorr and the output time was 2 minutes.

The methane plasma layer was post-treated with carbon dioxide plasma gas. The conditions were as follows: DC power was 5 watts, 500-600 volts; energy input per mass was 0.076 gigajoules / kg. The carbon dioxide gas flow rate was 2 standard cubic centimeters per minute (sccm); the pressure of the system was 50 mTorr; and the output time was 2 minutes.

The post-treated substrate was then electrodeposited with a cathode epoxyamine resin. Cathode electrodepositable coating is PPG E
5625 resin 4 parts (by volume), PPG E5605 pigment paste 1
Parts (volume) and 4 parts (volume) of deionized water. Electrodeposition of the cathode was performed under conditions well known to those skilled in the art. Electrodeposition was performed at 200 volts for 2 minutes. The electrodeposited thin film was then baked at 350 ° F. for 30 minutes.
The thickness of the thin film was about 25 microns.

The samples were then subjected to the corrosion test described above for about two weeks. Neither the adhesion nor the corrosion resistance of the above system applied to bare steel is comparable to current commercial electrodeposition primers applied to zinc phosphated steel. For example, the creep of this example was 2.3 mm, whereas currently commercially available electrodeposition systems for zinc phosphated steel have only about 0.5 mm of creep. However, we found that post-treatment with carbon dioxide plasma gas on the methane plasma thin film layer performed better than the same system without carbon dioxide post-treatment (2.3 mm creep without post-treatment and 4.8 mm creep). ). Adhesion was good by tape test (ASTM D3359).

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Young, Datsuk Jiyou Delaware, United States of America 19803. Wilmington. Paromino Court 4 (72) Inventor Yasuda, Hirotsugu Missouri, United States 65203. Colombia. Lake Point Rain 1004 (58) Field surveyed (Int. Cl. ⁶ , DB name) B05D 7/14 B05D 3/04 B32B 15/08 C23C 16/50

Claims (5)

(57) [Claims] 1. The following steps: (a) first treating a steel substrate with a reactive or insoluble gas plasma; (b) then depositing a thin film of an organosilane on the steel substrate; and (c) primer coating. Is applied on the organosilane thin film, wherein the primer coating is reactive with the organosilane thin film, comprising: 2. Deposition of the organosilane in step (b) in a vacuum chamber using direct current power having a cathode and at least one anode, wherein the steel substrate is a cathode, and at least one anode is a magnetic reinforcing member. 2. The method of claim 1 wherein the pressure in the vacuum chamber is less than 1.0 Torr. 3. The method according to claim 2, wherein in step (a) the steel substrate is treated with a reactive gas plasma. 4. In order to enhance the adhesion between the organosilane thin film and the primer coating, the organosilane thin film is post-treated between steps (b) and (c) to reduce the surface of the organosilane thin film. The method of claim 1, wherein the polarization is performed. 5. The method according to claim 4, wherein the post-treatment forms hydroxyl groups, acid groups or basic groups on the surface of the organosilane thin film.